Alkoxylation is a chemical reaction that involves the addition of an epoxide to another compound. The usual manifestation of this reaction is ethoxylation of alcohols (ROH), in which case ethylene oxide is the alkoxylating agent:

ROH + C₂H₄O → ROCH₂CH₂OH

Another industrially significant epoxide is propylene oxide (PO, OCH₂CHCH₃). PO is mainly used for alkoxylation to produce polyether polyols. The alkoxylation process is shown in simplified form:

ROH + n OCH₂CHCH₃ → R(OCH₂CHCH₃)_nOH

Polyols derived from PO have complex stereochemistry owing to the chirality of the propylene oxide. These polyols are used on a large scale to produce polyurethanes, by condensation with diisocyanates.^[1]